This study is designed to reveal the nature of the genetic control of morphogenesis in an eucaryotic organism, Drosophila melanogaster. The proposed research will entail an indepth genetic and developmental analysis on a previously identified homoeotic gene complex, the Antennapedia complex (ANT-C), which controls the ontogenic events leading to the formation of the anterior half of the organism. Further, a genetic dissection of the process of spermatogenesis will be carried out. This will be accomplished by the recovery of a large number of male sterile mutations throughout the genome which are temperature conditional for male fertility. These lesions will be characterized morphologically and biochemicallly in an attempt to more precisely define the genes controlling the production of sperm as well as the manner in which this control is effected. By a more complete understanding of the genetic control of ontogeny licited by homoeotic loci, as well as the morphogenesis involved in the production of an elongated from a nearly spherical cell, the spermatid, we can gain some insight into how the essentially two-dimensional information encoded in the gene is transformed into a three-dimensional organism.